Power press control means



Feb. 6, 1962 E. A. MUNSCHAUEIR, JR

POWER PRESS CONTROL MEANS Filed April 14. 1959 2 Sheets-Sheet 1 O O z 10O O /2 O O 56" 0 I NVENTOR.

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United States hatent 3,019,878 hDWE-li PRES CONTROL MEANS Edwin A.Munschauer, .ha, Snyder, N.Y., assignor to Niagara Machine 8; ToolWorks, Buffalo, N.Y. Fiied Apr. 14, 1959, Ser. No. 806,319 9 iaims.(til. 192144) This invention relates to control means for, powerpresses, press brakes, power shears and analogous machines.

The machine control means of the present invention relates particularlyto electrical control circuits and a control arrangement particularlyadapted for producing manually initiated single complete strokes orcycles of a machine. More particularly, the present invention providesmeans for effectively controlling single stroke machine operationwithmeans for simply and selectively compensating for certain varyingconditions which are incident to operating a machine of this generalcharacter at varying speeds.

It is common to provide so-called two-hand operating electrical pushbuttons which are spaced apart so that an operator must have his twohands on the push buttons at the time that a cycle of operation of amachine is initiated. The control circuit thus initiated may actuate asolenoid valve for operating a fluid pressure controlled clutch, aclutch and brake, or a combined clutch-brake mechanism. Various types ofclutches may be so controlled, such as positive. jaw clutches orfriction clutches. In the alternative, the eletrical impulse may beemployed in other ways for controlling machine starting and stopping.

In control circuits of this general type it is imperative that theoperator must keep his two hands on the push buttons during the firstportion of the cycle of operation to prevent his hands from being in anunsafe position or place. However, it is generally considered safe forthe operator to remove his hands from the push buttons after the machinehas gone through the first part of its cycle, say from 90 degrees to 120degrees of the cycle, since at normal speeds of operation it would beimpossible for the operator to move his hands from the push buttons intothe dies before the dies are completely closed if his hands are on thepush buttons for that portion of the first part of the stroke.

Furthermore, it is desirable that the operator be free to remove hishands from the push buttons when it is safe to do so, so that he mayprepare to remove a piece from the die, feed the next workpiece to thepress, or perform other similar operations. For these reasons thecontrol circuitry usually includes means for completing the strokeautomatically after the cycle has proceeded through a safe period asdescribed above.

Still further, conventional power press control circuits generallyinclude a non-repeat arrangement which insures stoppage of the press atthe end of a complete cycle even though the push buttons be held down.It is thus necessary for an operator to remove both hands from the pushbuttons before a succeeding cycle can be initiated by re-depressing thebuttons. This is commonly referred to as a non-tie-down feature whichprevents taping one or both of the buttons down to attempt to produceunauthorized continuous non-cyclic or one-hand operation.

From the foregoing it will be seen that the end of a cycle of operationis determined automatically and a common means for such determination isa cam member which controls a limit switch and moves in unison with thecrankshaft of a power press, press brake, power squaring shear or thelike. The end of a cycle of operation may be effected by opening orclosing of a limit switch which sets up conditions for clutchdisengagement or for clutch disengagement and brake engagement. In anyevent, there is an unavoidable time lag between the moment of switchactuation and the ultimate stopping of the machine parts which is knownin the art as drift." This drift in a given machine is fairly constantin angular magnitude for a given machine speed but is considerablygreater at higher speed operation than at low speed operation, andaccordingly provision for adjustment of one kind or another must be madeif a machine is subject to variations in speed of operation.

In machine control arrangements of this general class in the prior artit is general to design the limit switch control cam or cams for a givenspeed of operation. It is, therefore, necessary to effect a majorrearrangement if the speed of operation of the machine is to be changed,either by substituting a redesigned limit switch cam, or by providingmultiple plate cams which may be physically adjusted to vary their liftperiods to provide for varying points of switch opening or closure, orboth.

Means have been proposed to regulate the drive between a power presscrankshaft and limit switch mechanism for controlling power pressoperation, as in Bitler Patent No. 2,635,727, for instance. However,since these limit switches are usually mounted in the general vicinityof the crankshaft of the press they are high in the air and require aladder to make the necessary adjustment. The arrangement of the presentinvention provides ready selection of a proper limit switch combinationfrom the usual control panel of the press.

The present invention provides means whereby a simple selector switchlocated at and operable from the usual control panel of such machinevaries the time of clutch disengagement to occur at varying times beforethe end of a machine cycle to properly compensate for the drift of theparts from the instant of operation of the switch which institutesclutch disengagement or other machine-stopping operation to the timewhen the parts reach their desired position of rest.

In the form of the invention illustrated and described herein aplurality of such clutch stop limit switches are provided for selectiveinclusion in the machine control circuit by operation of the aforesaidselector switch. Each of the clutch stop limit switches is under thecontrol of a cam proportioned to operate the switch at predeterminedpoints in the machine cycle and the several cams are mounted upon asingle shaft which is connected to rotate in unison with the crankshaftor main drive shaft of the machine.

The multiple cam unit with the limit switches that are controlled andoperated directly by such cams will preferably be disposed upon themachine at a position where they may be conveniently driven from thedrive transmission means of the machine, with suitable electricalconductors extending therefrom to the machine control panel forcooperation with the control circuits and components of the machine.Preferably, in power press and similar use, the cams will be directlydriven from the crankshaft of the press at a one to one ratio.

A further prior art proposal for adjusting the making and breaking ofpower press control circuits is shown in Bitler Patent No. 2,520,709. Inall of these prior art adjustments it is not only necessary to reach aremotely controlled limit switch unit by the use of a ladder or thelike, but adjustment is generally effected by trial and error and thisis obviously very awkward and timeconsuming, particularly where the typeof adjustment necessitates opening the limit switch enclosure andreadjusting cams, commutators and the like by trial and error.

In the selector switch of the present invention the point at which theselection is made is conveniently located in the control panel which isdirectly in front of acme? the operator and adiustment is effected bythe mere flick of a switch to go from one range of operation to another.

A single specific embodiment of the principles of the present inventionis illustrated in the accompanying drawings and described in detail inthe following specification. However, it is to be understood that theprinciples of the invention are not limited to the precise form shownbyway of example and that the spirit and scope of the invention arelimited only as defined in the appended claims.

In the drawings:

FIG. 1 is a somewhat diagrammatic front elevational view of arepresentative power press with the rotating cam limit switch unit andthe control panel thereof illustrated in their respective positions; and

FIG. 2 is a wiring diagram of the control circuit arrangement of thepresent invention.

Referring to FIG. 1, a power press having the usual die-receiving bed 11and reciprocable slide or ram 12 is provided with a conventionalcrankshaft 13 for reciprocating the slide 12 and is further providedwith a control panel 14 within convenient reach of the operator forstarting and stopping the press and effecting other control functions.The numeral 15 designates a rotating cam limit switch of a type which isavailable commercially and which includes a series of cams on a commonshaft, each controlling the opening and closing of a limit switchincluded in the rotating cam limit switch unit. In the present instance,the operating shaft of this unit is designated 16 and is connected tothe crankshaft 13 of the press by a chain and sprocket connection 17 forrotation in unison with the crankshaft 13.

Referring particularly to the wiring diagram, the numeral 3h designatesa winding which controls an armature 31 which operates a valve or othercontrol means for the clutch and brake units of the power press and, asindicated in the diagram, these components may be located convenientlywith respect to the clutch and brake unit or units or at any otherconvenient point remote from the remaining electrical controlcomponents. As indicated in the preamble, the winding may control themachine starting and stopping function in other ways and clutch controland clutch and brake control are referred to herein as familiar means tothis end.

In FIG. 1 the numeral 20 indicates a conventional clutch-brake unitmounted on crankshaft 13.. A solenoid valve 21 controlledbyelectromagnet 30, 31 controls an operating air supply conduit 22 whichleads to the clutchbrake unit by way of a conduit 23. In the wiringdiagram a series of four cams 34, 35, 36 and 37 are shown, it beingunderstood that these cams rotate synchronously and will generally bemounted upon a common shaft of a unit known familiarly in this art as arotating cam limit switch, the shaft being rotated in unison with and ata one to one ratio with respect to the crankshaft of the power press.The limit switches controlled by the cams 34 through 37 comprise,respectively, normally open limit switches 38, 39 and it? and a normallyclosed limit switch 41. The three limit switches 38, 39 and 40 areclutch stop limit switches and are used selectively in the alternativeas will later appear. The fourth limit switch 41 is an anti-repeat limitswitch and its function in the control cycle will likewise presentlyappear. It will be noted that the four earns 34 through 37 and the limitswitches 38 through 4-1 controlled thereby are a part of the unit 15shown in FIG. 1 and are generally remotely located with respect to theother control means, which latter will now-be described.

A pair of supply conductors 45 and d6 energize the control circuits andthus ultimately the winding 39 which directly controls the clutch or theclutch and brake of the power press. Conductors 47 and 43 lead from oneside of the power supply and include spaced pairs of switches 51, 52, 53and 54. The switches 51 and 52 of conductor 4.7 are normally closed andthe switches 53 and 54 of conductor 58 are normally open. The switches51 and 53 are controlled by a common push button 56 and the switches 52and 54 are controlled by a common push button 57. The push buttons 56and 57 are spaced to require two-hand operation thereof as is well knownin this art.

One side of each of the limit switches 38, 35?, 4t} and 41 is energizeddirectly from supply conductor 45 and the other side of each of theselimit switches leads back to the control portion of the circuit by meansof conductors designated respectively 60, 61, 62 and 63. A selectorswitch at the control panel of the press is designated 65 andselectively connects any of the conductors 6t), 61 and 62 to a conductor66 to render any of the three limit switches 38, 39 and 4% effective incontrolling the terminal point of energization of winding 30 in a mannerand for a purpose which will presently appear.

Conductor 47, in addition to the normally closed,

push-button-opened switches 51 and 52, contains normally closed switches79 and 71 and a solenoid winding 72 and thence leads back to theopposite conductor 46 of the power supply. Conductor 48, in addition tothe normally open, push-button-closed switches 53 and 54, includes anormally open switch 74 which is closed when winding 72 is energized,and conductor 48 also includes a winding 76 which controls certainswitches in a manner which will presently be described, whereuponconductor 48 returns to the opposite conductor 46 of the power supply.

The conductor 66 which leads from the selector switch as and is thuscontrolled by one or another of the switches 38, 39 and 4%, includes apair of normally open switches 77 and '78 and thence connects withconductor 43 to lead back to supply conductor 46, also by way of thesolenoid winding 76. The conductor 63 which leads from and is controlledby the anti-repeat limit switch 74 includes a normally open switch '80,which is likewise closed by energization of winding 72 of conductor 47,and thence leads to conductor 47 at a point between switch 71 thereofand winding 72 thereof.

The circuit which directly energizes the clutch and brake controlsolenoid winding 30 when the proper conditions exist in the controlcircuit comprises a conductor 82 from supply conductor 45 and a returnconductor 83 which includes a pair of normally open switches 84 and 85and then returns to the opposite supply conductor 46, in the presentinstance jointly with the return portion of conductor 47. A furtherswitch control solenoid winding 87 connects with conductor 66 betweenthe switches 77 and 78 thereof by way of a conductor 36 and has itsopposite side connected to the return portion of conductor 47 asillustrated in the wiring diagram.

In the wiring diagram the several cams 34 through 37 are illustrated inthe positions which they assume at top dead center of the crankshaft ofthe press, that is, their positions when the crankshaft is at restbetween operating cycles.

It will be noted that the cams 34, 35 and 36 are similar excepting thatthe end of the rise portion of each of these cams occurs at a differentpoint. In cam 34 the rise ends a relatively short distance before topdead center, possibly ten degrees. In cam 35 the end of this riseportion occurs some 5% degrees before top dead center, whereas in cam 36the end of the rise occurs approximately degrees before top dead center.

Thus the three cams are respectively contoured to initiate clutchdisengagement and brake operation at points spaced variously from theend" of the desired stroke of the machine to allow for the varyingdegrees of drift in slow, medium and high speed operation. The followingoperation of the control structure and circuits will be discussed by wayof example in connection with the slow speed cam 34 and the limit switch38 controlled thereby, it being noted that selector switch 65 is in aposition wherein limit switch 38 is included in the control structurewhereas limit switches 39 and 40 are temporarily eliminated from thecontrol circuits.

It may be noted that the control circuit illustrated in the wiringdiagram shows only that portion of a machine control circuit which iseffective and operative to produce single stroke cycles of a machine,with automatic termination of the cycles arranged and provided for, aswill appear later herein. In an actual complete control circuitarrangement there will be additional circuit means provided forso-called jogging or inching of the press and also for continuousnon-cyclic operation. These latter two modes of operation are employedin the alternative with the single stroke operation which is here underconsideration and need not be further considered in this disclosure.

It will be noted that energization of the clutch and brake controlsolenoid winding 30 is ultimately, finally and directly determined byclosure of the two switches 84 and 85, the circuit for winding 30 beingfrom supply conductor 45 through conductor 82, winding 30, conductor 83which includes switches 84 and 85 in series, and thence back to theopposite supply conductor 46 by way of the return portion of conductor47. Since both switches 84 and 85 must be closed to energize andmaintain energization of clutch and brake solenoid winding 30,

the windings 87 and 76 which operate to close the switches 84 and 85must be energized to maintain the operating cycle by way of winding 30.

In an ordinary cycle of operation an operator depresses the manual pushbuttons 56 and 57 by two-hand operation, thus opening switches 51 and 52of conductor 47 and closing the switches 53 and 54 of conductor 48.

At this beginning point in the cycle of operation, winding 72 ismaintained energized, despite the opening of switches 51 and 52, by aholding circuit, and switches 74 and 80 are therefore held closed. Theholding circuit is from conductor 45 through the normally closed antirepeat limit switch 41, conductor 63, switch 80 and thence throughwinding 72 and the return portion of conductor 47 back to the oppositesupply conductor 46.

The closure of switches 53 and 54 establishes a circuit through Winding'76 which opens switch 71 and closes switches 78 and 85 and closure ofthe switch 78 establishes a circuit through winding 87 by way ofconductor 48 through the now closed switches 53, 54 and 74, and thencethrough a portion of conductor 48, conductor 66, switch 78 and conductor86. With the energization of the windings 76 and 87 in this manner theclutch and brake operating winding 30 is maintained energized but itwill be noted that release of either of the buttons 56 or 57 during thisbeginning portion of a cycle will break the circuit of winding 76through conductor 48, thus opening switch 85, to deenergize winding 30.

After a press has proceeded through a certain portion of the cycle thedies thereof advance toward a closed position a suflicient degree sothat an operator can no longer get his hands therein and thus thetwo-hand push button control may be released after the press hasoperated through a predetermined portion of the cycle, say, forinstance, 90 degrees as in the presently illustrated instance.

Accordingly, at the 90-degree point in the operation, cam 34 (or eitherof cams 35 or 36 if the selector switch happens to be set appropriately)closes switch 38 so that the clutch control winding 30 will bemaintained energized until a predetermined end point in the cycle,despite release of the push buttons 56 and 57 andconsequent opening ofswitches 53 and 54. This end point of energization of the winding 30, asindicated above, is determined by allowing an unenergized period at theend of the cycle sufficient to allow for the time lag in clutch releaseand/or brake operation, known in the art as drift.

This holding circuit which becomes established by operation of cam 34(in the illustrated position of the selector switch) is by way ofconductor 45, limit switch 38, conductor 66, selector switch 65,conductor 66 including the two closed switches 77 and 78, and thence byway of the return portion of conductor 48, through winding 76 to theother supply conductor 46.

At the time when limit switch 38 takes over in the above fashion,winding 87 is also energized by the circuit comprising conductor 45,limit switch 38, conductor 66, selector switch 65, conductor 66, switch77 and conductor 86 through the winding 67 and thence to the oppositesupply conductor 46.

With as much of the operation as has thus far been described, thebuttons 56 and 57 could be held depressed to continue energization ofthe winding 30 beyond the rise of the cam 34 to effect continuousrunning of the machine, which cannot be permitted. It would thus bepossible for an operator to tape the two buttons down and achievecontinuous running against regulations and safety precautions, or hecould vtape one button down and employ a one-hand operation which islikewise hazardous.

To prevent this is the function of cam 37 and an antirepeat relayarrangement which is under the control of switch 41. When the press haseffected approximately 180 degrees of its cycle of operation, the riseportion of cam 37 opens switch 41 which has been serving to maintainenergization of the anti-repeat winding 72. Upon such deenergizationswitches 74 and assume their normally open positions and winding 72cannot again be energized excepting by return of both of the buttons 56and 57 to their released positions wherein they close switches 51 and 52and to effect such reenergization of winding 72 these buttons mustremain in their released position beyond the end of the period ofenergization of the winding 36 as determined by the end of the rise ofthe cam 34 (in the illustrative instance). At the end of the rise of cam34 the windings 76 and S5 become deenergized as previously described andnormally closed switches 70 and 71 thus close to complete thereenergization of winding 72 and render possible the subsequentinstitution of a new cycle of operation by a further joint depression ofthe buttons 56 and 57.

I claim:

1. In a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit means for maintaining such energization after apredetermined initial period, a normally open switch in said firstcircuit means and manual push button means'for closing the same toinitiate a machine cycle, a plurality of parallel switches in saidsecond circuit means and a selector switch for including one or anotherof said plurality of switches in said second circuit means, a pluralityof synchronously rotating cams driven from said machine, each of saidcams being adapted to close one of said plurality of switches at apredetermined point in the machine cycle and open the same before theend of a cycle of machine operation, the switch opening points of saidcams being variously spaced from the end of a machine cycle tocornpensate for varying degrees of drift of the machine at variousoperating speeds, and anti-repeat means comprising a cam rotatable withthe aforesaid cams and a switch opened and closed thereby during eachmachine cycle to open said first circuit means and prevent reclosurethereof until the push button means is released and reclosed at the endof a cycle of operation.

2. In a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for theelectromagnetic'means, a first circuit means for energizing saidoperating circuit and a second circuit means for maintaining suchenergization after a predetermined initial period of energizationinstituted by said first circuit means, normally open switch means insaid first circuit means and manual push button means for closing thesame to initiate a machine cycle, a plurality of 8 parallel switches insaid second circuit means and a selector switch for including one oranother of said plurality of switches in said second circuit means aplurality of synchronously rotating cams driven from said machine, eachof said cams being adapted to close one of said plurality of switches ata predetermined point in the nachinecycle and open the same before theend of a cycle of machine operation, the switch opening points of saidcams being variously spaced from the end of a machine cycle tocompensate for varying degrees of drift of the machine at variousoperating speeds, and anti-repeat means comprising a cam rotatable withthe aforesaid cams and a switch opened and closed thereby during eachmachine cycle to open said first circuit means and prevent re-closurethereof until the push button means is released and reclosed at the endof a cycle of operation.

3. in a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit eans for maintaining such euergization after apredetermined initial period, a normally open switch in said firstcircuit means and manual push button means for closing the same toinitiate a machine cycle, a plurality of parallel switches in saidsecond circuit means and a selector switch for including one or anotherof said plurality of switches in said second circuit means, and aplurality of synchronously rotating cams driven from said machine, eachof said cams being adapted to close one of said plurality of switches ata predetermined point in the machine cycle and open the same before theend of a cycle of machine operation, the switch opening points of saidcams being variously spaced from the end of a machine cycle tocompensate for varying degrees of drift of the machine at variousoperating speeds.

4. in a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit for maintaining such energization after a prede terminedinitial period, a pair of normally open switches in said first circuitmeans and a pair of spaced manual push button means for closing the sameto initiate a machine'cycle, a plurality of parallel switches in saidsecond circuit means and a selector switch for alternatively includingone or another of said plurality of switches in said second circuitmeans, a plurality of synchronously rotating cams driven from saidmachine, each of said cams being adapted to close one of said pluralityof switches at a predetermined point in the machine cycle and open thesame before the end of a cycle of machine operation, the switch openingpoints of said cams being variously spaced from the end of a machinecycle to compensate for varying degrees of drift of the machine atvarious operating speeds, and anti-repeat means comprising a. camrotatable with the aforesaid cams and a switch opened and closed therebyduring each machine cycle to open said first circuit means and preventreclosure thereof until the push button means is released and reclosedat the end of a cycle of operation.

5. In a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit means for maintaining such energization after apredetermined initial period, a pair of normally open switches in saidfirst circuit means and a pair of spaced manual push button means forclosing the same to initiate a machine cycle, a plurality of parallelswitches in said second circuit means and a selector switch foralternatively including one or another of said plurality of switches insaid second circuit means, a plurality of synchronously rotating camsdriven from said machine, each of said cams being adapted to close oneof said plurality of switches at a predetermined point in the machine.cycle 8 and open the same before the end of a cycle of machineoperation, the switch opening points of said cams being variously spacedfrom the end of a machine cycle to compensate for varying degrees ofdrift of the machine at various operating speeds.

6. in a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit means for maintaining such energization after apredetermined initial period of energization instituted by said firstcircuit means, normally open switch means in said first circuit meansand manual push button means for closing the same to initiate a machinecycle, a plurality of parallel switches in said second circuit means anda selector switch for including one or another of said plurality ofswitches in said second circuit means, and a plurality of synchronouslyrotating cams driven from said machine, each of said cams being adaptedto close one of said plurality of switches at a predetermined point inthe machine cycle and open the same before the end of a cycle of machineoperation, the switch opening points of said cams being variously spacedfrom the end of a machine cycle to compensate for varying degrees ofdrift of the machine at various operating speeds.

7. In a. control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit means for alternatively energizing said operatingcircuit, a pair of normally open switches in series in said firstcircuit means and a pair of spaced manual push buttons for closing thesame to initiate a machine cycle, a plurality of parallel switches insaid second circuit means and a selector switch for including one oranother of said plurality of switches in said second 0' -cuit means, aplurality of synchronously rotating cams driven from said machine, eachof said cams being adapted to close one of said plurality of switchesand open the same during a cycle of machine operation, the switchopening points of said cams being variously spaced from the end of amachine cycle to compensate for varying degrees of drift of the machineat various operating speeds.

8. 'In a control system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit means for alternatively energizing said operatingcircuit, normally open switch means in said first circuit means andmanual push button means for closing the same to initiate a machinecycle, a plurality of parallel switches in said second circuit means, aplurality of synchronously rotating cams driven from said machine, eachof said cams being adapted to close one of said plurality of switchesand open the same during a cycle of machine operation, the switchopening points of said cams being variously spaced from the end of amachine cycle to compensate for varying degrees of drift of the machineat various operating speeds and a selector switch for including one oranother of said plurality of switches in said second circuit means.

9. In acontrol system for machines, electromagnetic means for startingand stopping the same, an operating circuit for the electromagneticmeans, a first circuit means for energizing said operating circuit and asecond circuit means for alternatively energizing said operatingcircuit, normally open switch means in said first circuit means and amanual push button means for closing the same to intiate a machinecycle, a plurality of parallel switches in said second circuit means anda selector switch for including one or another of said plurality ofswitches in said second circuit means, a plurality of synchronouslyrotating cams driven from said machine, each of said cams being adaptedto close one of said plurality of switches and open the same during acycle of machine operation, the switch opening point-s of said camsbeing variously spaced from the end of a machine cycle to compensate forvarying degrees of drift of the machine at various operating speeds, andanti-repeat means comprising a cam rotatable with the aforesaid cams anda switch opened and closed thereby during each machine cycle to opensaid first circuit means and prevent re-closure thereof until the pushbutton means is released and reclosed at the end of a cycle ofoperation.

References Cited in the file of this patent UNITED STATES PATENTS BundyNov. 24, Dean May 26, Geiger Apr. 13, Longfield Apr. 23, Bleeze May 1Simpson Aug. 19, Hadley May 12,

